1. Field of the Invention
This invention relates to a heat exchanger with coated fins which dissipate heat from a tubular fluid transporting system.
2. Description of the Prior Art
The use of fins attached to fluid containing tubes to dissipate heat from a contained liquid is well known. Generally, a series of tubes carry heated liquid and form a cooling system. The tubes have metal fins attached thereto which form heat dissipating means. The fins are generally made of aluminum or copper or the like. The common air conditioning unit or automobile radiator is a simple example of such a heat exchange unit.
The fins may be elongated, thin strips of aluminum. The width and length of the fins vary depending upon the number, diameter and configuration of the tubes. Generally, the fins may be force fit to the tubes or may be adhered thereto by solder or other means.
In order to provide anti-corrosion protection and ultra violet light resistance for the fins, it has been found advantageous to provide a coating on the surface of the fins. This coating also may produce a decorative effect.
One prior art method of providing such a coating on the fin is by spraying the coating on the fin after the assembly of the tube and the fin. This procedure is followed to prevent having an undesirable insulating film covering the tube/fin contact area which would reduce the operating efficiency of the unit.
Some of the difficulties with this procedure are the labor cost of applying the coating by spray or dipping, the equipment cost including spray tanks and ovens and the disposition of waste and other expensive steps.
In general in the assembled structure the fins are closely spaced and separated by the depth of the collar, usually about 1/8 inch apart, and so it is impossible to uniformly spray the coating on the finished unit since the atomized spray is travelling parallel to the fin surface.
Because of the difficulty in drying a non-uniformly applied coating, it is conventional to use a low solids, high volatile solvent based coating. The exposure of the paint line to fire and explosion and the extra cost of protection make this process undesirable.
Another method of coating the fin stock is to coat the full surface of both sides of the fin stock as it is unreeled from a large roll. This procedure is discussed in U.S. Pat. No. 4,588,025 which discloses the continuous application of a hydrophilic coating on both surfaces of an aluminum fin stock. This latter process does not solve the problem of the presence of a layer of the coating at the tube/fin contact area.
The present invention relates to a process which applies a protective coating in spaced stripes on the opposite surfaces of a sheet of fin stock as it is unwound from a larger roll. The fin stock is then cut in longitudinal strips so that for each strip there is an area along each edge which is coated and a central area which is uncoated. The uncoated central area is perforated and formed to receive one or more tubes to form a heat exchanger, while the outside edge areas act as heat dissipaters. The coating at the outside edge area also acts as a protective barrier against corrosion. The uncoated central area contacts the outside of the fluid-carrying tubes so that there is bare metal to metal contact.
It is therefore an object of the present invention to provide a novel heat exchanger which has a protective coating along the outer edge areas only.
It is another object of the present invention to provide a novel heat exchanger which will not have a coating layer between the fins and the tubes which carry the fluid.
It is still another object of the present invention to provide a novel heat exchanger in which the process of coating the fins of the heat exchanger after assembly is avoided.
It is yet another object of the present invention to provide a novel heat exchanger which can have the edge areas of the fins coated with a water-based coating by a simple and economical process.